Earticle

본 연구에서는 국내 스마트 베타 ETF를 대상으로 추적오차, 샤프지수 및 가격괴리율 분석을 통해 스마트 베타 ETF의 성과와 가격효율성을 분석한다. 또한 코로나 19 발생 이전과 이후 기간에서의 성과와 가격효율성을 비교 분석한다. 연구의 주요 결과는 다음과 같다. 첫째, 추적오 차의 값은 매우 작았고 유의하지 않은 것으로 나타났다. 회귀분석에 의한 분석에서는 스마트 베타 ETF가 통계적으로 기초지수를 잘 추적하지 못하는 것을 보여주었으나 차이는 매우 작았으며, 코로나 19 이후 기간에서의 추적오차가 이전 보다 더 크게 나타났다. 둘째, 벤치마크 성과에 대한 회귀분석 결과 스마트 베타 ETF의 일부 종목에서만 초과수익률을 기록하였다. 셋째, 샤프지수 분석 결과 스마트베타 ETF는 전체기간에 서는 지수 ETF보다 낮았으나, 코로나 19 이후 기간에서는 코로나 19 발생 이전 기간보다 높았고 지수 ETF 보다도 높은 것으로 나타났다. 넷째, 스마트 베타 ETF의 가격괴리율은 전반적으로 작고 음(-)의 값으로 할인현상이 더 많이 나타났으며, 지수 ETF 보다 작았다. 또한 코로나 19 발 생 이후 기간에서의 가격괴리율이 이전 기간보다 더 큰 것으로 나타났다. 이를 통해 국내 스마트 베타 ETF는 코로나 19 발생으로 인한 시장의 변동성이 심한 시기에 성과가 상대적으로 우수하다고 볼 수 있으나 이러한 결과는 일부 스마트 베타 ETF 에서만 나타났다. 따라서 국내 스마 트 베타 ETF 투자를 통해 항상 초과성과를 얻을 수 있는 것은 아니라는 사실을 유추할 수 있었고, 투자 실행에 앞서 스마트 베타 ETF의 주요 특성에 대한 학습과 주의가 필요하다고 하겠다.

This study analyzes the performance and price efficiency of smart beta ETFs through an examination of their tracking error, Sharpe ratio, and price deviation rate. It also compares their performance and price efficiency before and after the onset of COVID-19. The main findings are as follows. First, tracking error values were very small and statistically insignificant. Regression analysis indicated that smart beta ETFs did not statistically track their underlying indices well, though the difference was very small, and tracking error was larger in the post-COVID-19 period. Second, regression analysis of benchmark performance showed that only some smart beta ETF holdings recorded excess returns. Third, the Sharpe ratio analysis revealed that smart beta ETFs had lower Sharpe ratios than index ETFs over the entire period. However, during the post-COVID-19 period, their Sharpe ratios were higher than both the pre-COVID-19 period and index ETFs. Fourth, the price deviation rate of smart beta ETFs was generally small and predominantly negative, indicating a greater tendency toward discounting, and the deviation rate was smaller than that of index ETFs. This suggests that domestic smart beta ETFs demonstrated relatively superior performance during periods of high market volatility caused by COVID-19. However, this result was only observed in some smart beta ETFs. Therefore, it can be inferred that investing in smart beta ETFs does not always guarantee excess returns. Learning about the key characteristics of smart beta ETFs is required before executing investments.

본 논문에서는 지면반사를 이용한 크로스아이 재밍에 의해서 발생되는 모노펄스 레이다의 추적오차를 분석한 다. 크로스아이 재밍은 위상과 진폭이 다른 두 신호를 동시에 레이다로 송신하여 레이다 추적 시스템에 오차를 발생 시키는 방법이다. 모노펄스 레이다가 지형 바운스에 의해서 발생되는 크로스 아이 재밍신호를 수신하면 고각 방향으 로 추적오차가 발생 한다. 다중반사가 존재하는 저고도 환경에서 추적 레이다 수신기에서는 재머에서 송신된 신호가 직접 경로와 반사 경로 두 신호가 도달하여 그 경로 차에 의해 오차가 발생한다. 지형 바운스 재밍은 단일 재머를 이용하여 할 수 있는 장점이 있으나 재밍에 영향을 미치는 공간은 지형 반사각과 지형의 산란 정도에 의해서 제한된 다. 본 연구는 해상에서 저고도로 날아오는 미사일이나 항공기로부터 함정을 보호하기 위해서 유용하게 활용될 수 있을 것으로 판단된다.

In this paper, the tracking error of monopulse radar caused by cross-eye jamming using terrain bounce is analyzed. Cross-eye jamming is a method of generating an error in a radar tracking system by simultaneously transmitting two signals with different phases and amplitudes. When the monopulse radar receives the cross-eye jamming signal generated by the terrain bounce, a tracking error occurs in the elevation direction. In the presence of multipath, this signal is a combination of the direct target return and a return seemingly emanating from the target image beneath the terrain surface. Terrain bounce jamming has the advantage of using a single jammer, but the space affecting the jamming is limited by the terrain reflection angle and the degree of scattering of the terrain. This study can be usefully used to protect ships from low-altitude missiles or aircraft in the sea.

본 논문에서는 재귀형 크로스아이(retrodirective cross-eye) 재머 신호와 레이다 반사 신호 비(Jamming and radar return Signal Ratio: JSR)에 따른 모노펄스 레이다의 추적 오차의 변화를 분석하였다. 레이다 추적 오차를 계산하기 위한 방법으로 크로스아이 재머 이득(Gc)이 사용되었고, 재머 이득과 재머 신호와 레이다 반사 신호의 비(JSR)의 관계를 수식으로 표현하였다. 모노펄스 레이다와 재머 사이의 조우각과 JSR을 동시에 변화 시키 면서 레이다 추적 오차를 분석하였다. 그리고 재머 두 신호간의 위상(Φ) 차이와 JSR의 변화를 분석 한 결과 두 재머 신호 위상 차이가 180◦에 가까워질수록 추적 오차가 커지고 JSR이 20dB이상이 되면 추적 오차가 일정 수준 을 유지하게 되는 것을 볼 수 있다. 본 연구는 레이다 반사 신호의 비(JSR)에 따른 모노펄스 레이다의 추적 오차에 대한 결과를 제시하였고 추적 방향, 두 재머 신호 위상차, 두 재머 신호 크기 비율 등에 따른 복합적인 추적오차 분석 결과를 제시하였다.

In this paper, we analyze the tracking errors of monopulse radar according to the JSR of retrodirective cross-eye and radar skin return signals. The cross-eye jammer gain(Gc) is used to calculate the radar tracking errors, and the relationship between the jammer gain and the JSR is represented mathematically. We analyze the radar tracking errors by varying the tracking angle and JSR. Analysis results of the phase difference(Φ) and amplitude ratio(a) between the two jammer signals and the changing JSR show that the closer the phase difference of the two jammer signals is to 180, the greater the tracking error and it shows that if the JSR is above 20dB, the tracking errors no longer increase. This work presents an effective utilization of retrodirective cross-eye jammers through various tracking error analyses based on the JSR, tracking angles, two-jammer phase differences and amplitude ratios of two-jammer signals.

본 연구는 국내 시장에 상장된 인버스 ETF 상품의 일별자료를 활용하여 인버스 ETF의 추적오차와 괴리율을 분석하였으며 주요 분석결과는 다음과 같다. 첫째, 추적오차분석 결과 추적오차 값이 음(-)의 값으로 나타났으며 보유기간이 길어질수록 추적오차의 편차가 큰 것으로 나타났다. 둘째, 회귀분석을 통한 추적오차 결과에서 (-1)배율 인버스 ETF는 전체적으로 기초지수 수익률의 (-1)배에 미치지 못하였고, (-2)배율 인버스 ETF에서는 ETF의 일별수익률을 이용한 경우에는 기초지수 수익률의 (-2)배에 미치지 못하였으나 NAV 수익률의 경우에는 기초지수 수익률의 (-2)배와 유사하게 나타났으나 그 편차는 작았다. 셋째, 괴리율 분석 결과 괴리율의 평균은 모두 작고 통계적으로 유의한 음(-)의 값으로 나타났다. 또한 할인현상이 할증현상보다 더 많이 발생하는 것으로 나타났고, 기초지수가 상승한 날의 평균괴리율이 하락한 날보다 더 낮게 나타나 기초지수가 상승한 날 할인거래가 더 많이 발생하는 것으로 나타났다. 따라서 이를 통해 국내 인버스 ETF는 할인현상이 더 많이 발생하였고 괴리율은 0과 상이한 것으로 나타나 인버스 ETF의 효율적이지 않다고 판단할 수 있다. 또한 보유기간이 길수록 추적오차가 크고 인버스 ETF의 일별수익률이 기초지수의 수익률의 (-1)배 및 (-2)배에 다소 차이가 있고 유의적인 모습을 보여 기초지수를 잘 추적하지 못한 것으로 판단되며 이를 통해 인버스 ETF 투자를 통한 초과성과를 기대하는 것은 어렵다는 사실을 추론할 수 있다.

This study analyzed the tracking errors and price deviation of the inverse ETFs using daily data. The analysis results can be arranged in three main dimensions. First, the tracking error of inverse ETFs are negative(-) value except 1 day return. If analyzed using the ETF pricing return, statistically significant consideration was paid on the weekly return rate. And using the NAV return rate, it was significant in all cases. Also, the longer the holding period, the tracking error was also larger. Second, with respect to the tracking error of inverse ETFs, the results of regression analysis showed that (-1) multiple inverse ETFs are not successful in delivering the promised returns. And, (-2) multiple inverse ETFs in the case of using the daily ETF return are shown to be slightly less than (-2) multiple of the underlying index returns, but in the case of NAV return, it was similar to (-2) multiple of the underlying index returns. But, the difference was small and may be acceptable. Third, the price deviation analysis results show that the average of price deviation is small and statistically significant negative value. In addition, the discount appeared to occur more frequently than the premium, and more discount transactions were found on the day the underlying index went up. As a result, the inverse ETFs in Korea are more discounted and the price deviation is different from 0, which means that the inverse ETFs are not efficient. The longer the holding period, the larger the tracking error, and the daily return of inverse ETFs is somewhat different from (-1) multiple and (-2) multiple of underlying index returns. We can be inferred that it is difficult to expect excess returns through the inverse ETFs investment.

본 논문에서는 cross-eye의 두 재밍 안테나의 진폭 불일치로 인한 성능 저하를 고려한다. 진폭비의 불일치 는 기계적 결함에 따른 실제 진폭비와 명목상 진폭비의 차이가 정규분포를 갖는 랜덤변수로 모델링한다. 1차 테일러 전개와 2차 테일러 전개를 통한 해석적 성능분석이 제안된다. 실제 진폭비와 명목상 진폭비의 불일치가 발생한 Cross-eye 재밍의 성능 측정은 mean square difference (MSD)를 계산함으로서 측정된다. 해석적으로 유도된 MSD는 1차 테일러 전개 기반 시뮬레이션 기반 MSD 및 2차 테일러 전개 기반 시뮬레이션 기반 MSD와 해석 기반 MSD와 비교함으로써 검증된다. 계산비용이 높은 Monte-Carlo기반 MSD보다 해석 기반 MSD가 우수함을 보인다.

In this paper, performance degradation in the cross-eye jamming due to amplitude mismatch of two jamming antennas is considered. The mismatch of the amplitude ratio is modeled as a random variable with a normal distribution of the difference between the actual amplitude ratio and the nominal amplitude ratio due to mechanical defects. In the proposed analytic performance analysis, the first-order Taylor series expansion and the second-order Taylor series expansion is adopted. Performance measure of the cross-eye jamming is the mean square difference (MSD). The analytically derived MSD is validated by comparing the analytically derived MSD with the first-order Taylor series-based simulation-based MSD and the second-order Taylor series-based simulation-based MSD. It shows that the analysis-based MSD is superior to the Monte-Carlo-based MSD, which has a high calculation cost.

This paper is proposed a cell-specific reference signals (RSs)-based residual frequency offset (RFO) estimation scheme for 3GPP long term evolution (LTE) downlink in time-varying channels. For the computational efficiency and alleviate the effects of noise, two consecutive OFDM symbols which have same subcarrier index of cell-specific RSs are used. An analytical closed-form expression of the mean square error (MSE) of the post-FFT based RFO synchronization scheme is presented in terms of time-variant fading channels. In this paper, our analysis is compared to simulation results for demonstrate. Simulations are carried out within the LTE frequency division duplex (FDD) downlink systems.

It is the first and most important step in the detection of satellite navigation deception attack. For the detection of the regenerative deception attack, a method based on carrier phase tracking spectrum analysis is proposed. The simulation experiment results show that this method can be used in the case that the false alarm probability is no more than 0.5%, and the detection probability is almost 100%. The method is not necessary for the transformation of the hardware, the signal processing module in the software receiver can be added to the corresponding processing module, and the detection of the deception attack can be realized.

Tracking error performance is investigated for the typical maneuvering pattern of the anti-ship missile for tracking filters based on IMM filter in both clear and cluttered environments. Threatening targets to a navel vessel can be categorized into having three kinds of maneuvering patterns such as Waver, Pop-Up, and High-Diver maneuvers, which are classified according to launching platform or acceleration input to be applied. In this paper, the tracking errors for three kinds of maneuvering targets are represented and are investigated through simulation results. Studying estimation errors for each maneuvering target allows us to have insight into the most threatening maneuvering pattern and to construct the test maneuvering scenario for radar system validation.

Monopulse active homing radar requires velocity and angle information of target to track fast moving target. Target velocity can be estimated by measuring the frequency shift between transmitted and received frequencies. Angle information is obtained by measuring boresight error. Measurement of doppler frequency component in received signal is done through FFT analysis and interpolation algorithm for fine tuning. Boresight errors in azimuth and elevation axes are proportional to the power of each difference channel relative to sum channel. The target signal power in difference channel is estimated more precisely by measuring the power of FFT result cell of maximum ...

The study reported deals with investigating the feasibility of control strategy for a serial rigid link manipulator that applies impulsive torques at the joints. The strategy is illustrated for a planar three rigid link manipulator. An impulse-based concept which uses successive torque impulses on rigid link as the controller for motion correction was introduced. This control strategy was tested over the entire trajectory to demonstrate that the tracking error could be reduced effectively. The best condition for minimizing the tracking error with the least impulse input at each joint is investigated by considering one design and one operating parameter. The first was the damping in the system, and the second was the sampling time during operation. The results show that this approach can provide useful guidance for the design and control of robot manipulators that require minimum impulse feedback for accurate tracking.

The design and implementation of a high performance PID (Proportional Integral & Differential) style controller with zero-phase error tracking property is considered in this article. Unlike a ball screw driven system, the controller in a direct drive system should provide a high level of tracking performance while avoiding the problems due to the absence of the gear system. The stiff mechanical element in a direct drive system allows high precise positioning capability, but relatively high tracking ability with minimal position error is required. In this work, a feasible position controller named 'Unified PID controller' is presented. It will be shown that the function of the closed position loop can be designed into unity gain system in continuous time domain to provide minimal position error. The focus of this work is in two areas. First, easy gain tunable PID position controller without speed control loop is designed in order to construct feasible high performance drive system. Second, a simple but powerful zero phase error tracking strategy using the pre-designed function of the main control loop is presented for minimal tracking error in all operating conditions. Experimental results with a s-curve based position pattern commonly used in industrial field demonstrate the feasibility and effective performance of the approach.

This work is concerned with the problem of tracking a maneuvering target. In this paper, an error monitoring and recovery method of perception net is utilized to improve tracking performance for a highly maneuvering tar-get. Many researches have been performed in tracking a maneuvering target. The conventional Interacting Multiple Model (IMM) filter is well known as a suboptimal hybrid filter that has been shown to be one of the most cost-effective hybrid state estimation scheme. The subfilters of IMM can be considered as fusing its initial value with new measurements. This approach is also shown in this paper. Perception net based error monitoring and recovery technique, which is a kind of geometric data fusion, makes it possible to monitor errors and to calibrate possible biases involved in sensed data and extracted features. Both detecting a maneuvering target and compensating the estimated state can be achieved by employing the properly implemented error monitoring and recovery technique. The IMM filter which employing the error monitoring and recovery technique shows good tracking performance for a highly maneuvering target as well as it reduces maximum values of estimation errors when maneuvering starts and finishes. The effectiveness of the pro-posed method is validated through simulation by comparing it with the conventional IMM algorithm.

This paper describes weld seam tracking and error compensation methods of automatic plasma arc welding system designed for the corrugation panel that consists of a linear section and a curved section with various curvatures. Realizing automatic welding system, we are faced with two problems. One is a precise seam tracking and the other is an arc length control. Due to the complexity of the panel shape, it is difficult to find a seam and operate a torch manually in the welding process. So, laser vision sensor for seam tracking is equipped for sensing the seam position and controlling the height of a torch automatically. To attain more precise measurement of an arc length, we measure the 3D shape of the panel and analyze error factors according to the various panel states and caused errors are predicted through the welding process. Using that result, compensation algorithm is added to that of arc length control and real time error compensation is achieved. The result shows that these two methods work effectively.

This study investigates the influence of second language (L2) proficiency on error detection skills in L2 readers. Previous research has shown that advanced L2 learners outperform basic or intermediate learners in error detection tasks, particularly for subject-verb disagreement errors. However, it remains unclear if L2 proficiency extends to other error types. The present study explores the processing difficulties encountered by L2 readers when confronted with grammatical errors involving tense disagreement, article omission, word order, and nonwords. Eye-tracking data were collected to examine error sensitivity among L2 learners at different proficiency levels (basic, intermediate, and advanced). The findings reveal that L2 proficiency has a significant effect on error sensitivity, with advanced learners demonstrating higher sensitivity across various error types. However, the study finds no significant differences in error sensitivity for illegal nonwords among the proficiency levels. The presence of an error-checking task enhances error sensitivity, especially for advanced learners.

This paper describes the antenna alignment method of the tracking antenna system for LEO satellite. The purpose of the antenna alignment is to reduce the angular error due to the structural alignment and the monopulse null point alignment error. The angular error of 3 axis tracking system is the key performance parameter that should be minimized to accurately track satellite movement. The angular error is analyzed via a simulation and boresight measurement. The simulation is done with formulas to be derived from vector concept for 3-axis movement. The formulas of the structural alignment are verified by comparing the formula result with the field measurement. Also, the angular error due to monopulse null shift is obtained via boresight measurement. Based on the analyzed and measured results, the antenna alignment was performed and was verified via tracking test of operating LEO satellite.

We therefore aimed to identify the cause of failure of CT due to an error in BTS andto suggest an appropriate preventive method. Subjects underwent BTS-CT angiography andabdominal examinations in two university hospitals using a 64-detector CT scanner. An automaticBTS was used to time the start of the scanning when the injected contrast medium reached thethreshold level in the ROI. Errors in bolus tracking were divided into patient-related and machinerelatederrors. Among 2,000 patients who underwent BTS-CT, error was observed in 15 cases, inwhich the bolus tracking timing was shifted as a result of movement of the patient or respiratorychanges due to the rapid injection of contrast medium, which led to CT failure. To reduce CT-BTSfailures, the patient's position and the change in the position of the blood vessels due to the patient'sbreathing pattern should be carefully considered, and the ROI should be set to a sufficiently smallarea in the blood vessel.

With video compression standards such as MPEG-4, a transmission error happens in a video-packet basis, rather than in a macroblock basis. In this context, we propose a semantic error prioritization method that determines the size of a video packet based on the importance of its contents. A video packet length is made to be short for an important area such as a facial area in order to reduce the possibility of error accumulation. To facilitate the semantic error prioritization, an efficient hardware algorithm for face tracking is proposed. The increase of hardware complexity is minimal because a motion estimation engine is efficiently re-used for face tracking. Experimental results demonstrate that the facial area is well protected with the proposed scheme.

In order for electro-optical tracking system (EOTS) to have accurate target coordinate, accurate navigation results are required. If an integrated navigation system is configured using an inertial measurement unit (IMU) of EOTS and the vehicle's navigation results, navigation results with high rate can be obtained. Due to the time-delay of the navigation results of the vehicle in the EOTS and scale factor errors of the EOTS IMU in high-speed and high dynamic operation of the vehicle, it is much more difficult to have accurate navigation results. In this paper, an integrated navigation system of EOTS which compensates time-delay and scale factor error is proposed. The proposed integrated navigation system consists of vehicle's navigation system which provides time-delayed navigation results, an EOTS IMU, an inertial navigation system (INS), an augmented Kalman filter and integration Kalman filter. The augmented Kalman filter outputs navigation results, in which the time-delay of the vehicle's navigation results is compensated. The integration Kalman filter estimates position, velocity, attitude error of the EOTS INS and accelerometer bias, accelerometer scale factor error, gyro bias and gyro scale factor error from the difference between the output of the augmented Kalman filter and the navigation result of the EOTS INS. In order to check performance of the proposed integrated navigation system, simulations for output data of a measurement generator and land vehicle experiments were performed. The performance evaluation results show that the proposed integrated navigation system provides more accurate navigation results.

본 논문은 저가의 반사형 광학장치를 이용한 경제적인 BIPV 저집광 태양광 모듈 시스템에 대한 연구로, 화상인식 장치와 프로그램 계산 방식을 병행하여 태양광 추적 시스템을 향상시킴으로써 태양광 추적 정확도가 ±0.1°이내가 되도록 하였다. 이 시스템은 한 광원에서 발산된 빛의 명도를 추적하고, 명도의 분포 속에서 광원의 중심을 추적하는 트래킹방식이다. 그리고, 이를 통해 얻어진 데이터를 이용하여 다수개의 태양광발전장치를 동시에 구동시키는 제어방법을 갖추었으며, 발전장치의 동작결과 데이터를 수집해서 명령이행의 결과를 검증하는 네트워크 기반의 광원트래킹 다중제어 임베디드 시스템이다. 또한, 이를 실시간으로 모니터링 할 수 있도록 구현하였다.

In this paper, We developed the economic BIPV solar module system with the reflection-type optical devices. In conjunction with the image recognition device and program calculation method enhanced the solar tracking accuracy. It’s accuracy can be within ± 0.1 °. In this study, we made the system. This system traces the brightness of light emitted from the light source. And, in the distribution of brightness, we can find the center of the light source. Then, using the obtained data, the system can move a plurality of photovoltaic devices at the same time. Also, it is light source tracking multi-control embedded system of network-based with the results of operation of the device to collected data and to verify the results of fulfillment the command. In addition, it implemented to allow real-time monitoring.